Here's my advice (silly because most of my friends/family have babies older than Willa or have more than one child so they probably don't need much advice from a new mom) but here it is: complete sleep training before your baby can crawl and really roll and move around the crib.
Why? Because in just the few weeks that lapsed between sleep training attempt #1 and #2, Willa got much better at getting into the crawl position and scooting around and rolling over. So when we let her fuss, she would scoot around the crib, flip herself over (on accident, I think), and get stuck in crazy positions. We always felt bad so we'd have to go in and "fix" her. Silly little girl.